/*
 * Copyright (c) 2000, 2008, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 *
 *
 */
package javax.swing;

import java.util.Comparator;
import java.util.LinkedList;
import java.util.ListIterator;
import java.awt.Component;
import java.awt.ComponentOrientation;
import java.awt.Window;


/**
 * Comparator which attempts to sort Components based on their size and
 * position. Code adapted from original javax.swing.DefaultFocusManager
 * implementation.
 *
 * @author David Mendenhall
 */
final class LayoutComparator implements Comparator<Component>, java.io.Serializable {

  private static final int ROW_TOLERANCE = 10;

  private boolean horizontal = true;
  private boolean leftToRight = true;

  void setComponentOrientation(ComponentOrientation orientation) {
    horizontal = orientation.isHorizontal();
    leftToRight = orientation.isLeftToRight();
  }

  public int compare(Component a, Component b) {
    if (a == b) {
      return 0;
    }

    // Row/Column algorithm only applies to siblings. If 'a' and 'b'
    // aren't siblings, then we need to find their most inferior
    // ancestors which share a parent. Compute the ancestory lists for
    // each Component and then search from the Window down until the
    // hierarchy branches.
    if (a.getParent() != b.getParent()) {
      LinkedList<Component> aAncestory = new LinkedList<Component>();

      for (; a != null; a = a.getParent()) {
        aAncestory.add(a);
        if (a instanceof Window) {
          break;
        }
      }
      if (a == null) {
        // 'a' is not part of a Window hierarchy. Can't cope.
        throw new ClassCastException();
      }

      LinkedList<Component> bAncestory = new LinkedList<Component>();

      for (; b != null; b = b.getParent()) {
        bAncestory.add(b);
        if (b instanceof Window) {
          break;
        }
      }
      if (b == null) {
        // 'b' is not part of a Window hierarchy. Can't cope.
        throw new ClassCastException();
      }

      for (ListIterator<Component>
          aIter = aAncestory.listIterator(aAncestory.size()),
          bIter = bAncestory.listIterator(bAncestory.size()); ; ) {
        if (aIter.hasPrevious()) {
          a = aIter.previous();
        } else {
          // a is an ancestor of b
          return -1;
        }

        if (bIter.hasPrevious()) {
          b = bIter.previous();
        } else {
          // b is an ancestor of a
          return 1;
        }

        if (a != b) {
          break;
        }
      }
    }

    int ax = a.getX(), ay = a.getY(), bx = b.getX(), by = b.getY();

    int zOrder = a.getParent().getComponentZOrder(a) - b.getParent().getComponentZOrder(b);
    if (horizontal) {
      if (leftToRight) {

        // LT - Western Europe (optional for Japanese, Chinese, Korean)

        if (Math.abs(ay - by) < ROW_TOLERANCE) {
          return (ax < bx) ? -1 : ((ax > bx) ? 1 : zOrder);
        } else {
          return (ay < by) ? -1 : 1;
        }
      } else { // !leftToRight

        // RT - Middle East (Arabic, Hebrew)

        if (Math.abs(ay - by) < ROW_TOLERANCE) {
          return (ax > bx) ? -1 : ((ax < bx) ? 1 : zOrder);
        } else {
          return (ay < by) ? -1 : 1;
        }
      }
    } else { // !horizontal
      if (leftToRight) {

        // TL - Mongolian

        if (Math.abs(ax - bx) < ROW_TOLERANCE) {
          return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);
        } else {
          return (ax < bx) ? -1 : 1;
        }
      } else { // !leftToRight

        // TR - Japanese, Chinese, Korean

        if (Math.abs(ax - bx) < ROW_TOLERANCE) {
          return (ay < by) ? -1 : ((ay > by) ? 1 : zOrder);
        } else {
          return (ax > bx) ? -1 : 1;
        }
      }
    }
  }
}
